Ultrasonic diagnosis of cardiac performance using heart model chamber segmentation with user control

ABSTRACT

An ultrasonic diagnostic imaging system has a user control by which a user positions the user&#39;s selection of a heart chamber border in relation to two myocardial boundaries identified by a deformable heart model. The user&#39;s border is positioned by a single degree of freedom control which positions the border as a function of a single user-determined value. This overcomes the vagaries of machine-drawn borders and their mixed acceptance by clinicians, who can now create repeatably-drawn borders and exchange the control value for use by others to obtain the same results.

This application is the U.S. National Phase application under 35 U.S.C.§ 371 of International Application No. PCT/EP2016/054255, filed on Mar.1, 2016, which claims the benefit of U.S. Provisional Application Ser.No. 62/130,787, filed Mar. 10, 2015; U.S. Provisional Application Ser.No. 62/130,805 filed Mar. 10, 2015 and EP 15161561.4 filed Mar. 30,2015. These applications are hereby incorporated by reference herein.

This invention relates to medical diagnostic ultrasound systems and, inparticular, to the use of a heart model to segment myocardial boundarieswith user control to identify a heart chamber border.

Ultrasonic imaging is routinely used to diagnose cardiac performance bymeasurement of parameters such as ejection fraction and cardiac output.Such measurements require the volume of blood in a heart chamber atvarious phases of the heart cycle to be delineated in two or threedimensional images of a heart chamber. Typically measurements of thevolume of cardiac chambers, such as the left ventricle, have beengenerated by users hand tracing the endocardial boundary of the chamber.Such tracings are subject to significant variability due to differencesin the criteria different users utilize in determining where to locatethe tracing. Automatic methods have been developed to attempt toautomate this boundary tracing, such as the automated border tracingmethodology described in U.S. Pat. No. 6,491,636 (Chenal et al.) In thistechnique, anatomical landmarks of a chamber are located, including themitral valve plane corners and the apex of the heart chamber. One of aplurality of standard, expert-validated endocardial shapes are then fitto these landmarks. The automatically drawn border can then be manuallyadjusted by rubberbanding, by which the user moves control points on theborder to adjust its final position over the endocardium. Thisprocessing is done for images taken at the end systole and end diastoleheart phases. The two borders can be compared or subtracted to estimateejection fraction or cardiac output. For example, US 2009/0136109discloses to produce a myocardium thickness volume by comparing theidentified endocardial border (which defines an inner surface of themyocardium) and the identified epicardial border (which defines an outersurface of the myocardium). The myocardium thickness volume of US2009/0136109 is hollow, with the hollow space inside being the volume ofthe heart chamber. Ejection fraction can be estimated bywell-established methods such as an automated Simpson's algorithm (ruleof disks), to measure the fraction of the chamber volume ejected witheach contraction of the heart.

But automated image analysis methods do not always produce heart chamberdelineations that are acceptable to all users. This lack of success isdue in large part to the inability of the automatic methods toconsistently locate the border where any given user believes the bordershould be placed. Much of this poor performance is due to variationsbetween different users on what are the anatomical landmarks whichspecify where the true border lies.

It is an object of the present invention to provide users with a simpleautomated tool for delineating the location of an acceptable heartchamber border. It is a further object to do this by use of an automateddeformable heart model which is able to locate multiple myocardialboundaries. It is a further object that such delineations bestandardized, and capable of comparison and the production of repeatableresults among different users. Such results summarize the approach ofone clinician into a single value that can be understood andcommunicated to other clinicians who have the same tool.

In accordance with the principles of the present invention, a diagnosticultrasound system and method are described which diagnose cardiacperformance. Images of a chamber of the heart are acquired and an imageis segmented by use of a deformable heart model which is designed todelineate both an inner and an outer boundary of the myocardium, oralternatively several (3+) boundaries of the myocardium. A user controlis provided which enables a user to define the user's preferred chamberborder location in relation to one, both, or several of the segmentedboundaries. The user control provides a single value, a single degree offreedom, which the user varies to locate the border, such as apercentage of the distance relative to the segmented boundaries. Thesingle value can be shared with other users of the same tool, enablingother users to obtain the same results with other images, and hence astandardization of cardiac chamber border identification.

In the drawings:

FIG. 1 illustrates in block diagram form an ultrasonic diagnosticimaging system constructed in accordance with the principles of thepresent invention.

FIG. 2 is a block diagram illustrating border detection details of theQLQB processor of FIG. 1 in accordance with the principles of thepresent invention.

FIGS. 3a and 3b illustrate landmarks of the left ventricle which areuseful for border detection.

FIGS. 4a, 4b and 4c illustrate expert-derived endocardial border shapesused for automated border detection.

FIGS. 5a and 5b illustrates the delineation of epicardial andendocardial borders in images of the left ventricle.

FIG. 6 is a flowchart of the operation of a deformable heart model tofind heart borders in accordance with the present invention.

FIGS. 7a and 7b are cardiac images of the left ventricle at end diastoleand end systole in which the endocardial boundary and the interfacebetween the trabeculated myocardium and the compacted myocardium havebeen traced.

FIGS. 8a and 8b illustrate the end systole ultrasound image of FIG. 7bin which a user-defined border has been located at 0% and 100% of thedistance between the two heart boundaries delineated in FIG. 7 b.

FIG. 8c illustrates a cardiac image with a user-defined border islocated at 40% of the distance toward the compacted myocardium interfacefrom the endocardial tracing.

FIG. 8d illustrates a single degree of freedom user control inaccordance with the embodiments of the present invention, wherein theuser-defined border is located relative to several boundaries of themyocardium.

FIG. 9 illustrates user-defined heart chambers from biplane images whichare being volumetrically measured using the rule of disks.

FIG. 10 illustrates a user-defined heart chamber wire frame model from a3D ultrasound image preparatory to volumetric measurement.

Referring first to FIG. 1 an ultrasonic diagnostic imaging system 10constructed in accordance with the principles of the present inventionis shown in block diagram form. An ultrasonic probe 12 includes an array14 of ultrasonic transducers that transmit and receive ultrasonicpulses. The array may be a one dimensional linear or curved array fortwo dimensional imaging, or may be a two dimensional matrix oftransducer elements for electronic beam steering in three dimensions.The ultrasonic transducers in the array 14 transmit ultrasonic energyand receive echoes returned in response to this transmission. A transmitfrequency control circuit 20 controls the transmission of ultrasonicenergy at a desired frequency or band of frequencies through atransmit/receive (“T/R”) switch 22 coupled to the ultrasonic transducersin the array 14. The times at which the transducer array is activated totransmit signals may be synchronized to an internal system clock (notshown), or may be synchronized to a bodily function such as the heartcycle, for which a heart cycle waveform is provided by an ECG device 26.When the heartbeat is at the desired phase of its cycle as determined bythe waveform provided by ECG device 26, the probe is commanded toacquire an ultrasonic image. This enables acquisition at the enddiastole and end systole heart phases, for instance. The frequency andbandwidth of the ultrasonic energy generated by the transmit frequencycontrol circuit 20 is controlled by a control signal f_(tr) generated bya central controller 28.

Echoes from the transmitted ultrasonic energy are received by thetransducers in the array 14, which generate echo signals that arecoupled through the T/R switch 22 and digitized by analog to digital(“A/D”) converters 30 when the system uses a digital beamformer. Analogbeamformers may also be used. The A/D converters 30 sample the receivedecho signals at a sampling frequency controlled by a signal f_(s)generated by the central controller 28. The desired sampling ratedictated by sampling theory is at least twice the highest frequency ofthe received passband, and might be on the order of 30-40 MHz. Samplingrates higher than the minimum requirement are also desirable.

The echo signal samples from the individual transducers in the array 14are delayed and summed by a beamformer 32 to form coherent echo signals.For 3D imaging with a two dimensional array, it is preferable topartition the beamformer between a microbeamformer located in the probeand the main beamformer in the system mainframe as described in U.S.Pat. No. 6,013,032 (Savord) and U.S. Pat. No. 6,375,617 (Fraser). Thedigital coherent echo signals are then filtered by a digital filter 34.In the illustrated ultrasound system, the transmit frequency and thereceiver frequency are individually controlled so that the beamformer 32is free to receive a band of frequencies which is different from that ofthe transmitted band such as a harmonic frequency band. The digitalfilter 34 bandpass filters the signals, and can also shift the frequencyband to a lower or baseband frequency range. The digital filter can be afilter of the type disclosed in U.S. Pat. No. 5,833,613, for example.Filtered echo signals from tissue are coupled from the digital filter 34to a B mode processor 36 for conventional B mode image processing.

Filtered echo signals of a contrast agent, such as microbubbles, arecoupled to a contrast signal processor 38. Contrast agents are oftenused to more clearly delineate the endocardial wall in relation tocontrast agent in the blood pool of the heart chamber, or to performperfusion studies of the microvasculature of the myocardium as describedin U.S. Pat. No. 6,692,438 for example. The contrast signal processor 38preferably separates echoes returned from harmonic contrast agents bythe pulse inversion technique, in which echoes resulting from thetransmission of multiple differently modulated pulses to an imagelocation are combined to cancel fundamental signal components andenhance harmonic signal components. A preferred pulse inversiontechnique is described in U.S. Pat. No. 6,186,950, for instance.

The filtered echo signals from the digital filter 34 are also coupled toa Doppler processor 40 for conventional Doppler processing to producevelocity and power Doppler signals. The output signals from theseprocessors may be displayed as planar images, and are also coupled to a3D image processor 42 for the rendering of three dimensional images,which are stored in a 3D image memory 44. Three dimensional renderingmay be performed as described in U.S. Pat. No. 5,720,291, and in U.S.Pat. Nos. 5,474,073 and 5,485,842, all of which are incorporated hereinby reference.

The signals from the contrast signal processor 38, the B mode processor36 and the Doppler processor 40, and the three dimensional image signalsfrom the 3D image memory 44 are coupled to a Cineloop® memory 48, whichstores image data for each of a large number of ultrasonic images. Theimage data are preferably stored in the Cineloop memory 48 in sets, witheach set of image data corresponding to an image obtained at arespective time. The image data in a group can be used to display aparametric image showing tissue perfusion at a respective time duringthe heartbeat. The groups of image data stored in the Cineloop memory 48may also be stored in a permanent memory device such as a disk drive ordigital video recorder for later analysis. In this embodiment the imagesare also coupled to a QLAB processor 50, where the images are analyzedto automatically delineate borders of the heart, enabling a user to thenposition a border as the user believes most accurately indicates thetrue border of a chamber of the heart. The QLAB processor also makesquantified measurements of various aspects of the anatomy in the imageand delineates tissue boundaries and borders by automated border tracingas described in US patent publication no. 2005/0075567 and PCTpublication no. 2005/054898. The data and images produced by the QLABprocessor are displayed on a display 52.

FIG. 2 illustrates further details of the operation of the QLABprocessor to delineate a user-defined heart chamber border in accordancewith the principles of the present invention. A cardiac ultrasound imageis provided by a source of cardiac image data 60, which may be theCineloop memory 48, the 3D image memory 44, or one of image processors36, 38, or 40 of FIG. 1. The cardiac image is forwarded to an automaticborder detection (ABD) processor 62. The ABD processor may be a fullyautomatic or a semi-automatic (user-assisted) image processor whichdelineates a border of a chamber in a heart image, several of which aredescribed below. In a typical semi-automatic ABD system, the userdesignates a first landmark in the cardiac image with a pointing devicesuch as a mouse or a trackball, usually located on the ultrasound systemcontrol panel 70 or with a workstation keyboard, which manipulates acursor over the image. In the example of FIG. 3a , for instance, thefirst landmark designated is the medial mitral annulus (MMA) at thebottom of the left ventricle (LV) in the illustrated view. When the userclicks on the MMA in the image, a graphic marker appears such as thewhite control point indicated by the number “1” in the drawing. The userthen designates a second landmark, in this example, the lateral mitralannulus (LMA), which is marked with the second white control pointindicated by the number “2” in FIG. 3b . A line produced by the ABDprocessor then automatically connects the two control points, which inthe case of this longitudinal view of the left ventricle indicates themitral valve plane. The user then moves the pointer to the endocardialapex, which is the uppermost point within the left ventricular cavity.As the user moves the pointer to this third landmark in the image, atemplate shape of the left ventricular endocardial cavity dynamicallyfollows the cursor, distorting and stretching as the user-manipulatedpointer seeks the apex of the LV chamber, as shown in FIG. 5a . Thistemplate, shown as a white line in FIG. 5a , is anchored by the firstand second control points 1 and 2 and passes through the third controlpoint, which is positioned at the apex when the user clicks the pointerat the apex, positioning the third control point 3. Typical LV chamberborder templates are shown in FIGS. 4a, 4b, and 4c . These templates aredetermined from many expert tracings of the LV endocardial boundary inmany patients. The template 80 of FIG. 4a is an elongated templatetypical of many normal patients. The template 82 of FIG. 4b is morebulbous in shape, characteristic of many patients with congestive heartfailure. The template 84 is yet a third possibility, a more teardropshape. The template which best fits the three anatomical landmarksidentified by the user is selected by the ABD processor 62 and distortedto fit the three user-defined landmarks. When positioned and fitted tothe landmarks, the endocardial cavity template 80, 82, or 84 provides anapproximate tracing of the endocardium of the LV, as shown in FIG. 5a .In the example of FIG. 5a a black line which bisects the left ventriclefollows the pointer as it approaches and designates the apex. This blackline is anchored between the center of the line indicating the mitralvalve plane and the left ventricular apex, essentially indicating acenter line between the center of the mitral valve and the apex of thecavity.

Once the ABD processor 62 has found the endocardial lining of the LV, itthen attempts to find the epicardial boundary. This is illustrated inFIG. 5b , where the user has moved the cursor and clicked on the apex 4of the outside of the dark myocardium in the image. The images of FIG. 5are contrast-enhanced harmonic images in which the chamber of the LV hasbeen flooded with a contrast agent but the agent has not yet fullyperfused the myocardium, which is why the LV chamber appears very brightagainst the darker surrounding myocardium in this image. When the userclicks on the epicardial apex, the ABD processor, as before, selects anouter or epicardial template similar to the templates of FIG. 4 and fitsit to the epicardium as illustrated in FIG. 5b . The cardiac image nowhas both its endocardial boundary (line connecting 1, 3 and 2 markers),the blood pool-myocardium interface, and its epicardial boundary (lineconnecting 1, 4 and 2 markers), the outmost surface of the heart,delineated in the image by tracings produced by a graphics generator 66.

Instead of semi-automatic operation requiring user interaction, the ABDprocessor may delineate the border of the LV fully automatically asdescribed in the aforementioned U.S. Pat. No. 6,491,636. As explainedtherein, an image processor can be configured to find the mitral valvecorners and apex automatically, then fit a template to theautomatically-located landmarks. However, a preferred technique forautomatically delineating the myocardial borders is with a deformableheart model, as illustrated in FIG. 6. A heart model is aspatially-defined mathematical description of the tissue structure of atypical heart which can be fitted to the heart as it appears in adiagnostic image, thereby defining the specific anatomy of the imagedheart. Unlike a standard heart model designed to identify interiorstructures of the heart such as valves and chambers, the heart model ofthe present invention is designed to locate multiple myocardialboundaries, including both an inner endocardial boundary and an outerinterface between the trabeculated myocardium and the compactedmyocardium. The process of FIG. 6 begins with the acquisition of acardiac image at 90. The position of the heart is then localized in thecardiac image by processing the image data with a generalized Houghtransform at 92. At this point the pose of the heart has not beendefined, so misalignments in translation, rotation and scaling of theheart in the image data are corrected by use of a single similaritytransformation for the whole heart model at 94. Next at 96, the model isdeformed and affine transformations are assigned to specific regions ofthe heart. Constraints on the deformation are then relaxed by allowingthe heart model to deform with respect to the piecewise affinetransformation at 98, and the shape-constrained deformable model isresized and deformed so that each part of the model fits the actualpatient anatomy as shown in the image at the captured phase of the heartcycle, including both an inner and outer myocardial boundaries. Themodel is thus accurately adapted to the organ boundaries shown in thecardiac image, thereby defining the boundaries including the endocardiallining, the interface between the trabeculated myocardium and thecompacted myocardium, and the epicardial border. In a preferredimplementation of such a heart model, the interface between thetrabeculated myocardium and the compacted myocardium is found first, asthis typically appears as a well-defined gradient between a brightlyilluminated region and a region of moderate illumination in anultrasound image. The endocardial boundary is generally lesswell-defined in a heart model due to the desire to be able to find thevariable location of the less well-defined endothelial lining as itappears in an ultrasound image. Unlike the contrast-enhanced cardiacimages of FIGS. 5a and 5b , an unenhanced ultrasound image willgenerally exhibit a relatively sharp intensity gradient between therelatively high intensity echo tissue surrounding the myocardium and themedium intensity of the myocardium, and a relatively lesser gradientbetween the myocardium and the low intensity of the chamber's bloodpool. This mandates in favor of discriminating the outer myocardialborder first, then the inner endocardial boundary when diagnosing imagesacquired in the absence of a contrast agent. When the coordinates of aboundary have been found, they are communicated to the graphicsgenerator 66, which generates the traces that overlie the image in thecalculated positions.

FIG. 7 shows two ultrasound images, one with both boundaries of themyocardium outlined at end diastole (FIG. 7a ), and the second with bothmyocardial boundaries traced at end systole (FIG. 7b ). The compactedmyocardial boundary is traced in black and the endocardial boundary istraced in white in these images. With both boundaries thus identified byuse of the heart model, the user controls a chamber border delineator 64with a user control on control panel 70 to indicate a location betweenthe two myocardial tracings where the user believes the true chamberborder is located. In one implementation the user operates a singlevariable control by which the user can position the true endocardialborder at a location which is displaced a selected percentage of thedistance between the previously drawn endocardial boundary and thepreviously drawn interface between the trabeculated myocardium and thecompacted myocardium. FIG. 8a illustrates the end systole image of FIG.7b when the single variable control is set at 0%, and FIG. 8billustrates the same image with the user control set at 100%, in whichcase the white line border is located at the outside of the myocardium.The visual tracing of the user-defined border is also produced by thegraphics generator 66 in the system of FIG. 1 for overlay over theultrasound image. The user-set border is positioned at the called-forlocation as measured orthogonal to the endocardial tracing and at thecalled-for percentage of the distance between the two boundaries. Inthese examples the two myocardial boundary tracings are not shown forease of illustration, which is one possible implementation, although theautomatically drawn tracings could also be shown if desired.

FIG. 8c illustrates a situation in which the user has adjusted theuser-positioned border (shown as a white line) so that it is 40% of thedistance toward the epicardial or compacted myocardium interface fromthe endocardial tracing. This is done by moving a slider 100 left orright in its slot 102. As the slider is manipulated by the user, theuser-controlled border tracing 110 moves back and forth between the twoboundaries of the myocardium. In the example of FIG. 8c the slider 100is shown as a softkey control on the display screen which is manipulatedby a mouse or other user interface control, although the slide couldalternatively be a physical slider, knob or switch, or a trackball on aconventional ultrasound system control panel. The user control can alsobe implemented as a rocker control, toggle buttons, list box, or anumerical entry box. If the user has a preferred percentage for mostcases, this can be saved as a default value. In the example of FIG. 8cthe numerical percentage is displayed on the screen and changes as theslider 100 is moved. Also shown in FIG. 8d in an enlarged view 104 of aportion of the traced boundaries. The user clicks on a point of themyocardium of the image to the left, and that portion of the myocardiumappears in the enlarged view 104, with the user-manipulated border 110shown between the myocardial boundaries 106 (outer boundary) and 108(inner boundary). As the user manipulates the slider 100, the border 110moves between the two system-drawn boundaries 106 and 108. Theuser-manipulated border 110 can also be positioned using a range of morethan 100% as shown in the enlarged view 104′. The user-defined positionA (110′A) is positioned beyond the compacted myocardium boundary 106′and expressed in the range of more than 100%, while the user-definedposition C (110′C) is positioned within the endocardial tracing 108′ andexpressed in negative percentage range. The user-defined position B(110′B) positioned in between the endocardial and compacted myocardiumboundaries can be expressed in the range in between 0% and 100%.

Alternatively, for user convenience the user-manipulated (defined)border can be moved with respect to three outlines as illustrated inFIG. 8d (lower to the right view 104′): the compacted myocardiumboundary 106′ and endocardial boundary 108′, which correspond to thesame percentage 100% and 0% respectively as in the previous example; andan additional boundary 109′ corresponding to the percentage value of200%, wherein the additional boundary 109′ is located at the epicardialboundary. In the illustrated example, the slider 100 is adjusted at thevalue of 150% corresponding to the user-defined border 110′ position inbetween the compacted myocardium boundary 106′ and the epicardialboundary 109′. The alternative of the third boundary is addressing thefact that there is another boundary beyond the compacted myocardiumboundary (106′), which is the epicardial boundary (denoted in thisexample as the additional boundary), said epicardial boundary may bealso characterized by a noticeable and detectable gradient in theultrasound image, which could be used to constrain the single degree offreedom slider. This epicardial boundary can be also identified by theborder image processor.

The slider is a single degree of freedom control. The user sets theposition of the border 110 all around the chamber simply by setting thesingle value controlled by the slider. The value can be communicated toother users, who can obtain the same results by use of the same singlenumerical value.

FIGS. 9 and 10 illustrate how user-defined heart chamber borders of thepresent invention can be used to measure parameters such as cardiacoutput and ejection fraction. In the perspective view of FIG. 9 twouser-defined borders 210 and 212 of simultaneously acquired biplaneimages of the LV are shown on a base 220 which represents the mitralvalve plane. The apex marker of the two borders is shown at 230. In thisexample the image planes of the two biplane image borders are orthogonalto each other. The volume within the two borders 210 and 212 ismathematically divided into spaced planes 222 which are parallel to thebase plane 220. These planes intersect the left side of border 210 asshown at a,a and intersect the right side of border 210 as shown at c,c.The planes intersect the near side of tracing 212 as shown at b,b.

An ellipse is mathematically fit to the four intersection points a,b,c,dof each plane 222 as shown in FIG. 9. While curves or splines other thanellipses can be used, including arcs and irregular shapes, an ellipseprovides the advantage that Simpson's formula has been clinicallyvalidated when practiced with ellipses. The volume of the disks definedby the planes 222 and the ellipses can be calculated by the rule ofdisks to estimate the volume of the LV.

FIG. 10 shows a wire frame model constructed of a user-defined border ofa three dimensional heart chamber image. The horizontal sections 232,234, 236 of the wire frame are border lines which intersect verticalborder sections 210, 212 at intersection points a, b, c, and d. Thehorizontal sections are parallel to the mitral valve plane base 220. Thevolume within the wire frame can be determined by a modified rule ofdisks computation or other volumetric estimation technique. When avolume computed as shown in FIG. 9 or 10 for an end systole phase imageis subtracted from a volume calculated for an end diastole image anddivided by the same, the result is an ejection fraction estimation.

Other variations of the above will readily occur to those skilled in theart. Instead of a percentage quantification, the user-defined border canbe positioned an incremental distance from a manual or automaticallytraced boundary. The slider can be calibrated in distance so that theposition of a user-defined border is a user-determined number ofmillimeters offset from a reference boundary, for instance. Rather thanuse two traced boundaries, the user-defined border can be located inreference to a single boundary tracing, or can be at an interpolatedoffset from more than two boundaries.

The invention claimed is:
 1. An ultrasonic diagnostic imaging system fordetermining the border of a chamber of the heart in an ultrasound imagecomprising: a source of cardiac image data; a border detection processorthat receives the cardiac image data and comprises a deformable heartmodel configured to identify at least an inner boundary and an outerboundary of a myocardium in the cardiac image data; a chamber borderdelineator coupled to the border detection processor, wherein thechamber border delineator causes to be displayed a display trace of auser-defined border of a heart chamber in the cardiac image data,wherein the user-defined border is distinct from the inner boundary andthe outer boundary identified by the border detection processor; and auser control that enables the user to adjust a location of theuser-defined border by adjusting a location of the user-defined borderas a function of a distance between the inner boundary and the outerboundary.
 2. The ultrasonic diagnostic imaging system of claim 1,wherein the function of the distance between the inner boundary and theouter boundary is a percentage displacement of the location of theuser-defined border relative to the inner boundary and the outerboundary.
 3. The ultrasonic diagnostic imaging system of claim 2,wherein the deformable heart model is further configured to identify inthe cardiac image data an endocardium or a myocardium-blood poolinterface as the inner boundary, and an epicardium or an interfacebetween the trabeculated myocardium and the compacted myocardium as theouter boundary.
 4. The ultrasonic diagnostic imaging system of claim 2,wherein the user control further comprises a slider, a knob, a switch, atrackball, a rocker control, toggle buttons, a list box, a numericalentry box, a softkey control, or a physical control.
 5. The ultrasonicdiagnostic imaging system of claim 2, wherein the percentagedisplacement is zero when the location of the user-defined bordercoincides with the inner boundary, wherein the percentage displacementis one hundred when the location of the user-defined border coincideswith the outer boundary.
 6. The ultrasonic diagnostic imaging system ofclaim 5, wherein the percentage displacement is less than zero when thelocation of the user-defined border is within the inner boundary and thepercentage displacement is greater than one hundred when the location ofthe user-defined border is beyond the outer boundary.
 7. The ultrasonicdiagnostic imaging system of claim 1, wherein the source of cardiacimage data further comprises a memory device containing two-dimensionalcardiac images.
 8. The ultrasonic diagnostic imaging system of claim 7,wherein the source of cardiac image data is adapted to provide theborder detection processor with two-dimensional cardiac images includinga view of a left ventricle.
 9. The ultrasonic diagnostic imaging systemof claim 1, wherein the deformable heart model is further configured toinitially localize the position of the heart in the image data with ageneralized Hough transform.
 10. The ultrasonic diagnostic imagingsystem of claim 9, wherein the deformable heart model is furtherconfigured to determine the pose of the heart in the image data by useof a single similarity transformation.
 11. The ultrasonic diagnosticimaging system of claim 10, wherein the deformable heart model isfurther configured to deform with respect to piecewise affinetransformations.
 12. The ultrasonic diagnostic imaging system of claim1, further comprising a graphics generator, coupled to the boundariesidentified by the heart model, which is arranged to produce displaytraces of the inner and outer boundaries; and a display, coupled to thesource of cardiac image data and to the graphics generator, which isarranged to display a cardiac image with the display traces of the innerand outer boundaries.
 13. The ultrasonic diagnostic imaging system ofclaim 1, further comprising a graphics generator, coupled to the chamberborder delineator, which is arranged to produce the display trace of theuser-defined border; and a display, coupled to the source of cardiacimage data and to the graphics generator, which is arranged to display acardiac image with the display trace of the user-defined border.
 14. Theultrasonic diagnostic imaging system of claim 2, wherein the percentagedisplacement is based on a distance of the location of the user-definedborder from the inner boundary along a direction orthogonal to the innerboundary and a distance from the outer boundary to the inner boundaryalong said direction.
 15. The ultrasonic imaging system of claim 1,wherein the deformable heart model is configured to: identify aninterface between a trabeculated myocardium and a compacted myocardium;identify the outer boundary after the interface has been identified; andidentify the inner boundary after the outer boundary has beenidentified.
 16. The ultrasonic imaging system of claim 6, wherein theouter boundary is a compacted myocardium boundary of the myocardium andthe inner boundary of the myocardium is an endocardial boundary of themyocardium, wherein the deformable heart model is further configured toidentify an additional boundary, wherein the additional boundary is anepicardial boundary.
 17. The ultrasonic imaging system of claim 16,wherein the additional boundary constrains a range of the percentagedisplacement.
 18. The ultrasonic imaging system of claim 1, furthercomprising a processor configured to: generate a wire frame model of athree dimensional heart chamber based on the user-defined border; anddetermine a volume of the three dimensional heart chamber based on amodified rule of disks computation.
 19. The ultrasonic imaging system ofclaim 18, wherein the processor is further configured to: determine afirst volume of the three dimensional heart chamber at end systole;determine a second volume of the three dimensional heart chamber at enddiastole; and subtract the first volume from the second volume togenerate an ejection fraction estimation.